The use of composite structures has been steadily growing, particularly in those industries such as the aircraft industry where high strength, lightweight structures are especially desirable. Joints in these composite structures, such as between a panel or skin and a spar or rib are often subject to heavy tension stresses and can become a limiting factor in the composite structure. Various means have been used to strengthen these joints with varying degrees of success. It has been found that an especially effective joint can be prepared using an insert as practiced by this invention.